Context: Treatment with levothyroxine (LT4) that normalizes serum thyrotropin (TSH) is expected to restore lipid metabolism.

Objective: To assess statin utilization in LT4-treated patients through an observational drug utilization study.

Methods: Three sites were involved: (1) 10 723 outpatients placed on LT4 during 2006-2019 identified from the Clinical Research Data Warehouse of the University of Chicago; (2) ~1.4 million LT4 prescriptions prepared by primary care physicians during January- December 2018, identified from the IQVIA™ database of medical prescriptions in Brazil; (30 ~5.4 million patient interviews during 2009-2019, including ~0.32 million patients on
LT4, identified from the Fleury Group database in Brazil.

Results: On site 1, initiation of therapy with LT4 increased the frequency of statin utilization (19.1% vs 24.6%), which occurred ~1.5 years later (median 76 weeks) and, among those patients that were on statins, increased intensity of treatment by 33%, despite normalization of serum TSH levels; on site 2, after matching for sex and age, the frequency of statins prescription was higher for those patients using LT4: females, 2.1 vs 3.4% (odds ratio [OR] 1.656 [1.639-1.673]); males, 3.1 vs 4.4% (OR 1.435 [1.409-1.462]); and, on site 3, after matching for sex and age, the frequency of statin utilization was higher in those patients using LT4: females, 10 vs 18% (OR 2.02 [2.00-2.04]); males, 15 vs 25% (OR 1.92 [1.88-1.96]); all P values were <.0001.

Conclusion: Prescription and utilization of statins were higher in patients taking LT4. The reasons for this association should be addressed in future studies.

Use of Statins Among Patients Taking Levothyroxine: an Observational Drug Utilization Study Across Sites. Thaer Idrees, Wesley H. Prieto, Sabina Casula, Aswathy Ajith, Matthew Ettleson, Flavia A. Andreotti Narchi, Pedro S. T. Russo, Fernando Fernandes, Julie Johnson, Anoop Mayampurath, Rui M. B. Maciel, and Antonio C. Bianco. Journal of the Endocrine Society, 2021, Vol. 5, No. 7, 1–12 doi:10.1210/jendso/bvab038